swh:1:snp:c3bf2749e3476071fa748f67b0ffa2fdc5fe49d9
Tip revision: d5226fa6dbae0569ee43ecfc08bdcd6770fc4755 authored by Linus Torvalds on 27 January 2020, 00:23:03 UTC
Linux 5.5
Linux 5.5
Tip revision: d5226fa
utils.c
// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright (C) 2018 HUAWEI, Inc.
* http://www.huawei.com/
* Created by Gao Xiang <gaoxiang25@huawei.com>
*/
#include "internal.h"
#include <linux/pagevec.h>
struct page *erofs_allocpage(struct list_head *pool, gfp_t gfp)
{
struct page *page;
if (!list_empty(pool)) {
page = lru_to_page(pool);
DBG_BUGON(page_ref_count(page) != 1);
list_del(&page->lru);
} else {
page = alloc_page(gfp);
}
return page;
}
#if (EROFS_PCPUBUF_NR_PAGES > 0)
static struct {
u8 data[PAGE_SIZE * EROFS_PCPUBUF_NR_PAGES];
} ____cacheline_aligned_in_smp erofs_pcpubuf[NR_CPUS];
void *erofs_get_pcpubuf(unsigned int pagenr)
{
preempt_disable();
return &erofs_pcpubuf[smp_processor_id()].data[pagenr * PAGE_SIZE];
}
#endif
#ifdef CONFIG_EROFS_FS_ZIP
/* global shrink count (for all mounted EROFS instances) */
static atomic_long_t erofs_global_shrink_cnt;
#define __erofs_workgroup_get(grp) atomic_inc(&(grp)->refcount)
#define __erofs_workgroup_put(grp) atomic_dec(&(grp)->refcount)
static int erofs_workgroup_get(struct erofs_workgroup *grp)
{
int o;
repeat:
o = erofs_wait_on_workgroup_freezed(grp);
if (o <= 0)
return -1;
if (atomic_cmpxchg(&grp->refcount, o, o + 1) != o)
goto repeat;
/* decrease refcount paired by erofs_workgroup_put */
if (o == 1)
atomic_long_dec(&erofs_global_shrink_cnt);
return 0;
}
struct erofs_workgroup *erofs_find_workgroup(struct super_block *sb,
pgoff_t index, bool *tag)
{
struct erofs_sb_info *sbi = EROFS_SB(sb);
struct erofs_workgroup *grp;
repeat:
rcu_read_lock();
grp = radix_tree_lookup(&sbi->workstn_tree, index);
if (grp) {
*tag = xa_pointer_tag(grp);
grp = xa_untag_pointer(grp);
if (erofs_workgroup_get(grp)) {
/* prefer to relax rcu read side */
rcu_read_unlock();
goto repeat;
}
DBG_BUGON(index != grp->index);
}
rcu_read_unlock();
return grp;
}
int erofs_register_workgroup(struct super_block *sb,
struct erofs_workgroup *grp,
bool tag)
{
struct erofs_sb_info *sbi;
int err;
/* grp shouldn't be broken or used before */
if (atomic_read(&grp->refcount) != 1) {
DBG_BUGON(1);
return -EINVAL;
}
err = radix_tree_preload(GFP_NOFS);
if (err)
return err;
sbi = EROFS_SB(sb);
xa_lock(&sbi->workstn_tree);
grp = xa_tag_pointer(grp, tag);
/*
* Bump up reference count before making this workgroup
* visible to other users in order to avoid potential UAF
* without serialized by workstn_lock.
*/
__erofs_workgroup_get(grp);
err = radix_tree_insert(&sbi->workstn_tree, grp->index, grp);
if (err)
/*
* it's safe to decrease since the workgroup isn't visible
* and refcount >= 2 (cannot be freezed).
*/
__erofs_workgroup_put(grp);
xa_unlock(&sbi->workstn_tree);
radix_tree_preload_end();
return err;
}
static void __erofs_workgroup_free(struct erofs_workgroup *grp)
{
atomic_long_dec(&erofs_global_shrink_cnt);
erofs_workgroup_free_rcu(grp);
}
int erofs_workgroup_put(struct erofs_workgroup *grp)
{
int count = atomic_dec_return(&grp->refcount);
if (count == 1)
atomic_long_inc(&erofs_global_shrink_cnt);
else if (!count)
__erofs_workgroup_free(grp);
return count;
}
static void erofs_workgroup_unfreeze_final(struct erofs_workgroup *grp)
{
erofs_workgroup_unfreeze(grp, 0);
__erofs_workgroup_free(grp);
}
static bool erofs_try_to_release_workgroup(struct erofs_sb_info *sbi,
struct erofs_workgroup *grp)
{
/*
* If managed cache is on, refcount of workgroups
* themselves could be < 0 (freezed). In other words,
* there is no guarantee that all refcounts > 0.
*/
if (!erofs_workgroup_try_to_freeze(grp, 1))
return false;
/*
* Note that all cached pages should be unattached
* before deleted from the radix tree. Otherwise some
* cached pages could be still attached to the orphan
* old workgroup when the new one is available in the tree.
*/
if (erofs_try_to_free_all_cached_pages(sbi, grp)) {
erofs_workgroup_unfreeze(grp, 1);
return false;
}
/*
* It's impossible to fail after the workgroup is freezed,
* however in order to avoid some race conditions, add a
* DBG_BUGON to observe this in advance.
*/
DBG_BUGON(xa_untag_pointer(radix_tree_delete(&sbi->workstn_tree,
grp->index)) != grp);
/*
* If managed cache is on, last refcount should indicate
* the related workstation.
*/
erofs_workgroup_unfreeze_final(grp);
return true;
}
static unsigned long erofs_shrink_workstation(struct erofs_sb_info *sbi,
unsigned long nr_shrink)
{
pgoff_t first_index = 0;
void *batch[PAGEVEC_SIZE];
unsigned int freed = 0;
int i, found;
repeat:
xa_lock(&sbi->workstn_tree);
found = radix_tree_gang_lookup(&sbi->workstn_tree,
batch, first_index, PAGEVEC_SIZE);
for (i = 0; i < found; ++i) {
struct erofs_workgroup *grp = xa_untag_pointer(batch[i]);
first_index = grp->index + 1;
/* try to shrink each valid workgroup */
if (!erofs_try_to_release_workgroup(sbi, grp))
continue;
++freed;
if (!--nr_shrink)
break;
}
xa_unlock(&sbi->workstn_tree);
if (i && nr_shrink)
goto repeat;
return freed;
}
/* protected by 'erofs_sb_list_lock' */
static unsigned int shrinker_run_no;
/* protects the mounted 'erofs_sb_list' */
static DEFINE_SPINLOCK(erofs_sb_list_lock);
static LIST_HEAD(erofs_sb_list);
void erofs_shrinker_register(struct super_block *sb)
{
struct erofs_sb_info *sbi = EROFS_SB(sb);
mutex_init(&sbi->umount_mutex);
spin_lock(&erofs_sb_list_lock);
list_add(&sbi->list, &erofs_sb_list);
spin_unlock(&erofs_sb_list_lock);
}
void erofs_shrinker_unregister(struct super_block *sb)
{
struct erofs_sb_info *const sbi = EROFS_SB(sb);
mutex_lock(&sbi->umount_mutex);
/* clean up all remaining workgroups in memory */
erofs_shrink_workstation(sbi, ~0UL);
spin_lock(&erofs_sb_list_lock);
list_del(&sbi->list);
spin_unlock(&erofs_sb_list_lock);
mutex_unlock(&sbi->umount_mutex);
}
static unsigned long erofs_shrink_count(struct shrinker *shrink,
struct shrink_control *sc)
{
return atomic_long_read(&erofs_global_shrink_cnt);
}
static unsigned long erofs_shrink_scan(struct shrinker *shrink,
struct shrink_control *sc)
{
struct erofs_sb_info *sbi;
struct list_head *p;
unsigned long nr = sc->nr_to_scan;
unsigned int run_no;
unsigned long freed = 0;
spin_lock(&erofs_sb_list_lock);
do {
run_no = ++shrinker_run_no;
} while (run_no == 0);
/* Iterate over all mounted superblocks and try to shrink them */
p = erofs_sb_list.next;
while (p != &erofs_sb_list) {
sbi = list_entry(p, struct erofs_sb_info, list);
/*
* We move the ones we do to the end of the list, so we stop
* when we see one we have already done.
*/
if (sbi->shrinker_run_no == run_no)
break;
if (!mutex_trylock(&sbi->umount_mutex)) {
p = p->next;
continue;
}
spin_unlock(&erofs_sb_list_lock);
sbi->shrinker_run_no = run_no;
freed += erofs_shrink_workstation(sbi, nr);
spin_lock(&erofs_sb_list_lock);
/* Get the next list element before we move this one */
p = p->next;
/*
* Move this one to the end of the list to provide some
* fairness.
*/
list_move_tail(&sbi->list, &erofs_sb_list);
mutex_unlock(&sbi->umount_mutex);
if (freed >= nr)
break;
}
spin_unlock(&erofs_sb_list_lock);
return freed;
}
static struct shrinker erofs_shrinker_info = {
.scan_objects = erofs_shrink_scan,
.count_objects = erofs_shrink_count,
.seeks = DEFAULT_SEEKS,
};
int __init erofs_init_shrinker(void)
{
return register_shrinker(&erofs_shrinker_info);
}
void erofs_exit_shrinker(void)
{
unregister_shrinker(&erofs_shrinker_info);
}
#endif /* !CONFIG_EROFS_FS_ZIP */